Mr. D's right about diet playing a role, and one of our other members, Breukelen Advocaat, can tell you about gluten intolerance/celiac disease, which I believe I remember reading can cause ulcerations in severe cases. You'd typically also get gut pain/discomfort if that were happening. It also occurred to me that sometimes certain medicines can cause ulcerations, if that's what's happening to you (which you'd know if you were also having pain in your gut). Try watching what you're eating and also make sure you're getting enough fiber!